1. Field of the Invention
The present invention relates in general to an automotive seat and more particularly to a seat assembly having a seat slide device for sliding the seat to a desired position and latching the same at the desired position. More specifically, the present invention is concerned with a so-called "walk-in" mechanism incorporated with the seat slide devices, by which egress and ingress of a rear seat passenger is facilitated.
2. Description of the Prior Art
Hitherto, various types of seat slide devices have been proposed and put into practical use particularly in the field of motor vehicles. Some are of a type which is equipped with a so-called "walk-in" mechanism which, for facilitation of egress and ingress of a rear seat passenger, permits a forward movement of the seat when the seatback of the seat is inclined forward.
In order to clarify the task of the present invention, one of the conventional seat slide devices of the above-mentioned walk-in type will be described with reference to FIGS. 4, 5 and 6 of the accompanying drawings.
Referring to the drawings, particularly FIG. 6, there is schematically shown a seat slide device 10 to which the conventional walk-in mechanism is practically applied. The seat slide device 10 comprises two parallel stationary rails 12 (only one is shown) secured to a vehicle floor (not shown), two movable rails 11 (only one is shown) slidably disposed on the stationary rails 12 and mounting thereon a seat "S" (see FIG. 4), and roller and ball bearings 13a and 13b arranged between the coupled rails 12 and 11 to smooth the movement of the movable rails 11 relative to the stationary rails 12. One of the stationary rails 12 has an axially extending latch plate 14 secured thereto. The latch plate 14 is formed with a plurality of aligned notches 14a. Latchingly engageable with the notches 14a is a latch pawl member 20 which is pivotally connected to the movable rail 11 through a pivot shaft 20a. Although not shown in the drawing, a coil spring is disposed about the pivot shaft 20a to bias the same in a direction to bring the latch pawl member 20 into latching engagement with the notches 14a. Thus, when the latch pawl member 20 is pulled against the biasing force of the spring to assume its inoperative position (viz., the position "B" or "C"), the sliding movement of the movable rail 11 relative to the stationary rail 12 is permitted. While, when the latch pawl member 20 is engaged with selected one of the notches 14a, the movable rail 11 is latched to the stationary rail 12. Thus, under this condition, the seat on the movable rail 11 can not move any longer, that is, the seat is latched at a desired position relative to the vehicle floor.
The conventional walk-in mechanism is incorporated with the latch pawl member 20 in such a manner as will be described in the following.
As is seen FIGS. 4 and 5, the walk-in mechanism comprises a pivot shaft 6 through which a link member 4 is pivotally connected to a seat cushion 1 of the seat "S". The link member 4 is connected to a seatback 2 through a known reclining mechanism 5. Denoted by numeral 3 is a bracket through which a pivot shaft of the reclining mechanism 5 is connected to the seatback 2. The inclination angle of the seatback 2 relative to the seat cushion 1 is thus adjustable by pivoting the seatback 2 about the pivot shaft of the reclining mechanism 5. That is, the seatback 2 and the link member 4 can be locked with each other with a desired relative angle defined therebetween. As is shown in FIG. 5, the walk-in mechanism further comprises a holding pin 16 secured to the seat cushion 1 and a hook member 15 pivotally connected to the link member 4. Although not shown in the drawing, a control wire extends from the hook member 15 to a control lever which is mounted to the seatback 2. Thus, when, due to manipulation of the control lever, the hook member 15 is disengaged from the holding pin 16, the seatback 2 can pivot about the pivot shaft 6 forward together with the link member 4 keeping the desired relative angle between the seatback 2 and the link member 4. The link member 4 has a downward projection 4a to which a flexible transmission wire 7 is connected through a connecting pin 8. The wire 7 is slidably received in an elongate and bent tube 7a secured to a bottom portion of the seat cushion 1 and extends to the afore-mentioned latch pawl member 20 (see FIG. 6). Thus, when, with the hook member 15 kept disengaged from the holding pin 16, the seatback 2 is inclined forward about the pivot shaft 6 to its forward angular position as illustrated by the dot-dot-dash line in FIG. 4, the wire 7 is pulled toward the link member 4 thereby pivoting the latch pawl member 20 in the direction to disengage from the notches 14a of the plate 14. Upon this, the movable rail 11 (and thus the seat "S" mounted thereon) is moved forward to its foremost position by an action of a pull spring (not shown) which is arranged in the seat slide device in a known manner. Under this condition, egress and ingress of a rear seat passenger is easily made.
However, due to its inherency in construction, the above-mentioned seat slide device has the following drawbacks.
That is, the moved distance of the wire 7 changes largely depending on the position which the seatback 2 has assumed before execution of the walk-in operation. This will be well understood from FIG. 4 wherein two selected positions "I" and "II" of the seatback 2, which have been set by the reclining mechanism 5, are illustrated by the solid and dot-dash lines respectively. In order to achieve the walk-in operation with the seatback 2 assuming the position "I", the seatback 2 must incline forward by an angle "x", while when assuming the position "II", the seatback 2 must incline by a larger angle "y". As will be seen from FIG. 5, the angular difference (viz., y-x) thus produced brings about a difference in moved distance of the wire 7 which is directly connected to the link member 4.
However, as is seen from FIG. 6, the difference in moved distance of the wire 7 makes the determination of the effective length of the wire 7 difficult or at least troublesome. That is, when the wire 7 is set longer than a desired length, it tends to occur that the latch pawl member 20 fails to disengage from the notches 14a even when the seatback 2 is inclined to its foremost angular position, while, when the wire 7 is set shorter than the desired length, it tends to occur that, as is indicated by the arrow "C", the latch pawl member 20 is pulled excessively when the seatback 2 is inclined forward. Of course, these phenomena are disadvantageous in achieving a proper and smooth operation of the walk-in mechanism.